Smallpox is a serious, highly contagious, and sometimes fatal infectious disease caused by the variola virus, a member of the poxvirus family. Smallpox outbreaks have occurred from time to time for thousands of years, but the disease was effectively eradicated by 1977 after a successful worldwide vaccination program. After this disease was eliminated, routine vaccination against smallpox among the general public was stopped because it was no longer necessary for prevention. Consequently, a large fraction of the current human population has not been immunized against smallpox. As a result, a bioterrorist variola virus attack would be devastating. Importantly, were such an attack carried out, vaccination would be too slow to effectively arrest the rapid spread of smallpox in the targeted population. There is therefore a need for rapidly acting and effective compositions for treating smallpox infection.